there's no 450 limit
i don't have sources at hand, but AFAIRemenber there is a ~2000 chars limit for type1 messages and ~6000 for type2.
the type to be used is determined at runtime, it depends on the client on the other hand.
&RQ does not support direct connections ATM.
direct connections would break these limits.
DC means peer-to-peer communication beetwen clients.